1. Technical Field
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The present invention relates to predictive electric motor positioning devices and more particularly to automatic temperature control (ATC) systems using computer controlled electric motors and motor positioning algorithms for controlling motor operations Under normal vehicle power.
2. Background Art
Many computer controlled electric motor systems employ some control system method to perform motor movement functions and to determine proper motor operating parameters. Usually, a calibration-routine which determines various system limits occurs before normal motor control operations. If a normal motor operation problem develops, a fault routine operates to correct the problem or to terminate normal operations.
In prior ATC vehicle networks, electric motors control doors of the heater-ventilation-air conditioner units (HVAC). A calibration algorithm checks for full opening and closing of doors driven by the motors. A computer using controlling software moves the shaft of each door motor in succession in one direction until end-of-travel. Analog-feedback signals from potentiometers associated with each motor provide measured values for the position of each motor which the computer stores in memory. The computer, using the controlling software moves the shaft of each door motor in succession in the opposite direction to obtain and store another end-of-travel feedback signal value. The computer, a microcontroller unit (MCU) dedicated to the system, determines from this stored data whether the door feedback circuit operates properly. This approach defines potentiometer settings at end-of-travel positions but does not yield any information concerning time between ends-of-travel.
U.S. Pat. No. 5,369,342 dated Nov. 29, 1994 of the present inventors discloses a calibration system for performing calibration of a hybrid motor controlled network consisting of closed-loop and open-loop motor systems. This application teaches deriving and storing average ignition voltages and door movement times during ATC system door calibration operations. Such information factors in certain types of mathematical relationships are used in normal and fault operation to effect door movement.
In the past, during normal operation, the ATC system used a control algorithm to calculate a desired position for the motor. The motor control software would then move the motor in the correct direction and constantly monitor the motor analog feedback signal voltage until the value corresponded to the calculated desired position. Some systems use pulse width modulation (PWM) of the motor control signal to reduce the motor speed when approaching the desired position. This PWM approach for reducing motor speed would prevent the motor doors from travelling beyond the desired position.
This past system worked well, but it was highly feedback dependent. Hence, to reduce the dependency of the feedback circuits, for normal operation of the ATC system, it is desirable to utilize the stored average ignition voltages and door movement time. It is also desirable to operate a hybrid system containing close-loop (electric servo) and open-loop (single-ended) door motors without sacrificing effectiveness and creating a need for additional hardware.